Three of the world's most spectacular mountain ranges intersect in Pakistan’s north -- the Himalayas, the Hindu Khush and the Karakoram -- forming the largest reservoir of ice outside the poles. The country's mountainous north is home to more than 7,000 glaciers -- more than any region outside the poles -- but frequent, intense heat waves linked to climate change are causing them to melt, raising the risk of flash flooding. Melting glaciers swell lakes, which then burst their banks and unleash torrents of ice, rock and water in events known as glacial lake outburst floods (GLOFs). IMAGES AND SOUNDBITES ARRANGED IN SEQUENCES